1. Field of the Invention
The present invention relates to a film formation method, a film formation apparatus, and a method for using a film formation apparatus, for forming a silicon oxide film (SiO2 film) on a target object by use of an Si source gas and an oxidizing agent, and particularly relates to a semiconductor process technique. The term “semiconductor process” used herein includes various kinds of processes which are performed to manufacture a semiconductor device or a structure having wiring layers, electrodes, and the like to be connected to a semiconductor device, on a target object, such as a semiconductor wafer or a glass substrate used for an FPD (Flat Panel Display), e.g., an LCD (Liquid Crystal Display), by forming semiconductor layers, insulating layers, and conductive layers in predetermined patterns on the target object.
2. Description of the Related Art
In the manufacturing sequence of semiconductor devices, there is a process for forming an SiO2 film on a semiconductor wafer (which may be simply referred to as a wafer), such as a silicon wafer. In such a film formation process for forming an SiO2 film, a vertical film formation apparatus of the batch type is often used to form an SiO2 film on a plurality of semiconductor wafers together at a time by chemical vapor deposition (CVD) using an Si source and an oxidizing agent.
In recent years, owing to the demands for increased miniaturization and integration of semiconductor devices, it has been required to form an SiO2 film of higher quality at a low temperature of 400° C. or less. As a technique for fulfilling the demands, there has been proposed a technique for forming an SiO2 film by ALD (Atomic Layer Deposition) that alternately supplies an Si source gas and an oxidizing agent to laminate layers of an atomic layer level or molecular layer level (for example, Jpn. Pat. Appln. KOKAI Publication No. 2003-7700 (Patent Document 1)).
In film formation processes of an SiO2 film performed by CVD or ALD, a film formation process is repeated for a plurality of wafers. For example, in vertical heat processing apparatuses of the batch type, a wafer boat with a batch of wafers placed thereon is loaded into a process container, and a film formation process is performed on these wafers. Then, a wafer boat (or the wafer boat) with another batch of wafers placed thereon is loaded into the process container, and the film formation process is performed on these wafers. In this way, the film formation process is repeated a plurality of times.
However, as the thickness of films deposited on the inner surface of the process container is larger while the film formation process is repeated a plurality of times, the number of particles deposited on the wafers is suddenly increased. Particularly, in the case of ALD, which performs film formation at a lower temperature, this problem is prominent.
Jpn. Pat. Appln. KOKAI Publication No. 2006-351948 (Patent Document 2) and Jpn. Pat. Appln. KOKAI Publication No. 2008-140864 (Patent Document 3) disclose techniques to prevent particle generation due to film peeling, by reforming films deposited on the inner surface of the process container.
However, the techniques disclosed in the Patent Documents 2 and 3 are not arranged to solve problems about particles in film formation processes of an SiO2 film performed by CVD or ALD.